Component made of a fiber composite material and process for producing same

ABSTRACT

Fiber composite components can be formed by winding fibers along tracks of a winding spool of a winding core. The fibers may either be pre-coated with a curable resin, or the curable resin may be applied to the fibers after the fibers are wound along the tracks of the winding spool of the winding core. The curable resin may also and/or alternatively be applied to a mold that receives the fibers wound about the winding spool. The curable resin may then be cured, after which the winding spool and the winding core may be removed in order to release the fiber composite component. In some cases, the winding spool may be removed from the fiber composite component by moving the winding spool inwardly towards an inside of the winding core.

The present invention relates to a component from a fiber-composite material, having the features of the preamble of claim 1 or 2, and to a method for manufacturing such components, according to the preamble of claim 5.

In many assemblies, components in a fiber-composite construction assume structural tasks in which the tensile strength of the fibers is vital as well as in particular that the fibers run as precisely as possible in the direction of stress.

In the technical conception of components, in particular of components for motor vehicles, which support high forces, as for example the steering column, there is a conflict of objectives in terms of requirements for installation space, rigidity, weight, and costs. Components of the generic type are presently preferably made from steel, sheet metal, and cast aluminum or magnesium. Components, in particular also in motor vehicles, made from plastics materials and/or based on fiber technologies/fiber-composite technologies already exist. However, these components are either very expensive, or the technologies cannot be employed in the respective application because the requirements in terms of transmission of forces cannot be met.

Fiber-composite materials are composed of reinforced fibers which are embedded in a matrix. The general rule is that the specific rigidity of a fiber-composite material or of a hybrid material from metal and a fiber-composite material is higher than that of metal alone. The superior properties are only achieved by way of the interaction of both components. A multiplicity of manufacturing methods, in which the fibers which have been preimpregnated with a matrix material are processed, exist. One of the established manufacturing methods is the method of fiber winding. In the fiber-winding method the endless fiber strands (rovings) are wound onto a winding core in a continuous process. The fibers here are often soaked and wet-impregnated with a matrix resin during the same operational step, or non-soaked fibers which are soaked after the winding process by way of a resin-injection method are processed. The fiber-winding process is distinguished by high laminate quality and high precision in terms of the fiber-resin content and in terms of fiber orientation, while at the same time having a high degree of automation and being very economical.

A lattice-type component from a fiber-reinforced plastics material, and a method for manufacturing the same are disclosed in EP 1 268 164 B1. Manufacturing of the lattice-type component is performed by the fiber-winding method, depending on the predetermined stress or the stress to be expected. To this end, a number of winding spools around which the preimpregnated fibers are wound are provided on a winding plate. The cavities between the thus created external belt parts and the intermediate structure are, at least in regions, filled with a filler material. The filler material supports those portions of the lattice-type intermediate structure that are compression-loaded and prevents uncontrolled buckling when the calculated load of said portions is exceeded. Lattice-type structures are distinguished by their high level of stability. It is envisaged that these elements are employed as support beams, for example in a vehicle chassis, the filler material inter alia facilitating the absorption of energy in the event of a crash. The shape and the profile of the reinforcement of the support-beam component cannot be individually designed on account of the predetermined lattice-type structure. The reinforcement may indeed be adapted to the load by way of a variable number of fibers, but a specific design embodiment along force lines of a component is not possible.

It is therefore the object of the present invention to provide by way of fiber-composite technology individually molded components, in particular also components of motor vehicles, from a fiber-composite material, which have high strength properties and rigidity properties and are of low weight. Furthermore, a production method for components of this type, which enables a defined conception of the components, is to be provided.

This object is achieved by a method having the features of claim 1 or 2, and by a component having the features of claim 5. Advantageous refinements of the invention are represented in the dependent claims.

Accordingly, a method for manufacturing a component from a fiber-composite material, in particular a component for motor vehicles, is provided, the method comprising the following steps:

-   -   a) winding fibers along predetermined tracks about at least one         winding spool of a winding core;     -   b) introducing a curable resin into the fibers;     -   c) curing the resin and forming the fiber-composite component;     -   d) removing the at least one winding spool toward the inside         into the winding core;     -   e) removing the winding core and releasing the fiber-composite         component.

In a further step, the fitting of a corresponding functional group for a motor vehicle may be performed while installing the component from a fiber-composite material which is also referred to as a fiber-composite component. An example of a functional group of this type is presented in the form of a steering column assembly of a motor vehicle.

In one preferred embodiment, moving the wrapped winding core into a mold is performed after step a), and removing the fiber-composite component together with the winding core from the mold is performed after step c). The resin is then introduced into the mold in step b).

In one alternative embodiment, the fibers have already been soaked or coated with a curable resin prior to winding, so that ex post introduction of the curable resin may also be omitted. Accordingly, a slightly modified sequence which however leads to the same outcome results. In this alternative embodiment the method comprises the following steps:

-   -   a) winding fibers along predetermined tracks about at least one         winding spool of a winding core, wherein the fibers are soaked         with a curable resin;     -   b) curing the resin and forming the fiber-composite component;     -   c) removing the at least one winding spool toward the inside         into the winding core;     -   d) removing the winding core and releasing the fiber-composite         component.

In one preferred embodiment, moving the wrapped winding core into a mold is performed after step a), and removing the fiber-composite component together with the winding core from the mold is performed after step c).

Also in the alternative embodiment, a curable resin may be additionally introduced into the mold before the method step of curing the resin is performed.

Also in the alternative embodiment, the fitting of a corresponding functional group for a motor vehicle may be performed in a further step while installing the component made from a fiber-composite material which is also referred to as a fiber-composite component.

The application of the method is preferable for components or functional groups in a motor vehicle, which have to transmit large forces or torques. The application of the method for components which do not form closed sections is particularly preferable here. In this way, U-sections or W-sections or planar components may be readily represented by way of the method. Components which are disposed in the flux of force between the motor-vehicle superstructure and the body may in particular be readily represented.

Fiber strands are formed on account of the fibers having being wound.

Preferably, in a method step prior to winding, in order to be connected by way of the subsequent method steps to the fibers so as to form an integral component with the fiber-composite component, one or a plurality of functional elements are positioned at predetermined points on the winding core. The functional elements remain in the component, configuring interfaces and functional faces which cannot be wound in an efficient manner.

Preferably, it may moreover be provided that in a method step prior to winding, an auxiliary material, which keeps the fibers in shape and position until the latter are fixed by curing of the resin, is applied onto the winding core. This auxiliary may be a woven fabric or a cross-laid structure which likewise forms a fiber composite with the matrix and serves for receiving basic loads, for inducing loads, or as a force-free structure.

According to one preferred embodiment, the fiber-reinforced plastics material is a combination of various types of fiber structures having identically oriented fibers.

The component preferably has fiber strands, the fibers of which are oriented in a substantially straight line and so as to be substantially mutually parallel along a main direction of flux of force between a selection of in each case two functional elements by way of which the component is supported, wherein spatial regions in which no fibers and also no plastics material are disposed are configured between fiber strands which are thus configured. In other words, the fibers, gathered as fiber strands, are oriented so as to be mutually parallel as in a lattice support-beam structure. The proviso “substantially” relates to permissible deviations from linearity and parallelism in the range of a few angular degrees, certainly less than 5 or preferably less than 3 angular degrees.

In order for components such as, for example, the console of a steering column, of the pivot lever, or of the steering-spindle bearing unit to be represented, it is particularly preferable for three-dimensional fiber strands to be configured, wherein at least one of the fiber strands is disposed at an angle to that plane that is projected by at least two other fiber strands. Accordingly, at least one functional element is preferably disposed in another plane in relation to that plane that is projected by the at least two fiber strands.

Furthermore, individual fiber strands may be configured so as to be curved in a constantly differentiable manner, wherein the individual fibers within the fiber strand are oriented so as to be substantially mutually parallel. This is of advantage in particular when the flux of force has to be directed across various planes, in particular has to be directed around a fold or edge, and there is no functional element which is disposed in the flux of force provided on the component. On account of the constantly differentiable routing of lines, further transmission of force is performed at a reduced risk of buckling or notching.

Preferably, the component is made using a winding core which in order to complete the component or prior to fitting of the component is contained in the functional group which is separate from the component and is not contained in the functional group. This winding core has a contour which mirrors the profile of the fiber strands. On account thereof, in particular the configuration of constantly differentiable and curved fiber strands is readily enabled. The component according to the invention and also the functional group formed therefrom have very high rigidity and robustness, despite there being only a few fiber strands having large intermediate spaces which serve in forming the component. This becomes possible since the loads are absorbed either along the fiber strands or transversely to the fiber strands by way of adjoining components of the functional group. Accordingly, the component itself does not have to absorb the loads in all directions or itself to be resistant to the loads, respectively.

The envisaged functional elements of the component are preferably selected from the group including fastening elements, guides, motion limiters, bearings, and brackets for wiring looms.

In one further embodiment, the functional elements are sheet-metal lugs having openings, bores, or clearances. Sintered compacts or castings may also be integrated as functional elements of the components. Furthermore, other compacts from various metals or a plastics material may also be employed as functional elements. The method according to the invention is particularly flexible here.

One preferred embodiment of the invention will be explained in more detail hereunder by means of the drawings. As examples, components of a steering-column assembly will be illustrated here. However, the invention is also applicable to other components. In the drawings:

FIG. 1: shows a spatial illustration of a steering-column assembly from the prior art;

FIG. 2: shows a spatial illustration of a winding core having winding spools and functional elements;

FIG. 3: shows a schematic illustration of the winding operation;

FIG. 4: shows a spatial view of the winding core after the winding operation;

FIG. 5: shows a spatial view of the winding core from FIG. 4, with the tensioning direction indicated;

FIG. 6: shows an exploded drawing of the wound winding core with a mold;

FIG. 7: shows a spatial illustration of the closed mold;

FIGS. 8 and 9: show two spatial views of a console according to the invention;

FIG. 10: shows a spatial view of the console according to the invention from FIGS. 7 and 8, without functional elements; and

FIG. 11: shows a spatial illustration of a steering-column assembly according to the invention.

A steering column 1 which is known per se, having a steering spindle 2, a steering-column tube 3, a pivot lever 4, a console 5, and a control-rod part 6, is illustrated in FIG. 1. The steering spindle 2 is rotatably mounted in the steering-column tube 3. The steering-column tube 3 is guided in the pivot lever 4 so as to be displaceable along the longitudinal axis of the steering spindle 2. The pivot lever 4 is mounted in the console 5 so as to be pivotable about a pivot axis. The console 5 here may be fastened to fastening points 7 on the body (not illustrated). The rotation movement which is introduced by a driver via a steering wheel into the steering spindle 2 is introduced into the steering gear (not illustrated) via a cardan joint 8 and further control-rod parts 6. For enhanced driver comfort, the steering column 1 may be adjusted in height and length thereof. To this end, a fixing mechanism which comprises a tensioning apparatus is provided. The tensioning apparatus has a tension bolt 9, a tension lever 10, and a cam mechanism (not shown). The two cams of the cam mechanism are rotated counter to one another and the lateral walls of the console 5 are contracted by rotating the tension lever 10, on account of which a frictionally engaged tension fit between the side walls of the console 5 and the lateral faces of the pivot lever 4 and in turn with the lateral faces of the steering-column tube 3 is performed. Steering columns of this type are known from the prior art so that a precise illustration is dispensed with here. As an alternative to the example, mounting of the steering spindle 2 may also be performed in a steering-spindle bearing unit which is not configured so as to be tube-shaped and which may also be referred to as a sleeve unit. Likewise, fixing of the steering-spindle bearing unit or of the steering-column tube 3 in relation to the console may be illustrated to be, by means of a form-fit, for example a gear tooth system. Steering columns of this type, for example, are also included in the invention.

FIG. 2 shows a winding core 11 of a component according to the invention, here of a console 55, having a multiplicity of winding spools 12, 121, and functional elements 13. The functional elements 13 are positioned on the winding core 11 prior to winding process and during the winding operation are wrapped collectively with the winding core 11 along the winding spools 12, 121. In the context of the invention, the winding spools may not only be formed by simple cylindrical spools 12. Every mold 121 around which the rovings are wound is subsumed by the term “winding spool”. After the winding process has been terminated, the winding core 11 is removed, whereas the functional elements 13 remain in the component, configuring interfaces and functional faces which cannot be wound in an efficient manner. Such functional elements include, for example, fastening elements or bearings.

FIG. 3 schematically shows the method according to the invention which is preferably employed for manufacturing the components of a steering column from a fiber-reinforced plastics material. The representation of the console 55 is visualized in the example. However, the steering-column tube, or another steering-spindle bearing unit, or the slide, if existent, or any other load-transmitting component may also be configured by way of this technology. A fiber 14, which is held so as to be pretensioned, is drawn off from a supply package 15 and guided through an impregnation unit 16. The impregnation unit 16 may be configured as a dipping-tank device or, as is illustrated in an exemplary manner, as a roller impregnation device. The impregnated fiber 14, for forming the fiber strands 141, 142, is deposited by means of a guide unit 17, which is connected to a computer-controlled winding machine, on a winding core 11 of a console, which is moved in a synchronized manner with the guide unit 17. It can be seen in the example that the winding operation is performed in a three-dimensional manner, that is to say that the fibers are wound not only in one plane but that a three-dimensional fiber-strand structure is created. This winding operation is preferably performed without interruption, such that all fiber strands 141, 142 are formed by a single and continuous fiber 14.

The winding core 11, having the functional elements 13, is illustrated in the wrapped state in FIG. 4. The impregnated fiber which has been drawn off from the supply package as a roving is deposited according to a predetermined winding plan onto the winding spools 12, 121, and around the functional elements 13. The winding plan is to be determined so as to correspond to the geometry of the component. In the conception of the winding plan, the directions of the flux of force in the console are analyzed, and the strength properties and rigidity properties of the material are exploited in an optimal manner by depositing fibers 14 in a targeted manner in the direction of the flux of force in order for the fiber strands 141, 142, 143 to be formed. This is implemented by adapting the fiber-volume content, the fiber orientation, and the number of fibers so as to correspond to the flux of force. Moreover, the weight of the console is reduced on account of the targeted deposition of the fibers. At least one winding is carried out for producing the console. If a plurality of windings are carried out, the fibers may thus intersect from alternating directions at the intersection points, on account of which the strength in the transverse direction to winding is reinforced. Winding is carried out in a spatial manner. To this end, the winding core is rotated in a computer-controlled manner or is mounted on a rotation axis, such that the fibers can be guided about the core. It can be seen in the example (see also FIGS. 8, 9) how the winding spool 121 does not lie in that plane that is formed by the fiber strands 141 or the fiber strands 143. Correspondingly, during winding a fiber strand 142 which protrudes from the plane which is formed by the fiber strands 141 or the fiber strands 143 is formed.

It has to be considered in the winding plan that the fibers are guided in a straight line for as long as possible before the winding direction and thus the orientation of the fibers are changed. On account thereof, points or buckles of the fibers, which may cause breakage, are minimized. Under the same aspect tensioning of the fibers, as is shown in FIG. 5, may be provided in a further production step after winding.

The arrows in FIG. 5 indicate the tensioning directions of the winding core 11. Tension may be generated in a mechanical manner, for example, by displacement of the winding spools 12, or by way of elastic winding spools which yield during depositing and thereafter restore themselves. The fibers are pretensioned by the tension applied on the fibers, such that buckles in the fibers are reduced. This process increases strength and rigidity of the fiber-composite material in the direction of deposition.

The matrix of the fibers is cured after winding. In order for it to be shaped, the wrapped winding core 11 in the example is surrounded by a mold 18, as is illustrated in FIG. 6 and FIG. 7. The mold 18 illustrated here has two plates 19 which by means of screw or plug connections are in each case attached to one side of the winding core 11, so as to superimpose the wound part. The mold 18 here compresses the preimpregnated fibers between the plates 19 and the winding core 11, so as to acquire the desired shape. The cross section of the workpiece and the fiber-volume content can be influenced in this way. Curing of the workpiece in the mold 18 is thereafter performed by way of a heated mold, for example, or by placing the mold 18 in a continuous oven.

The mold and the winding core together with the winding spools are removed after curing. To this end, the winding core is configured such that the winding spools can be removed inwardly into the winding core and that the winding core is thereafter released for removal from the cured console.

The cured console 55 according to the invention is shown in FIG. 8 and FIG. 9. Apart from the structure from a fiber-composite material, which is formed by the fiber strands 141, 142, 143, the individual wrapped functional elements 13 can be seen. It can be seen in the example how the component includes two parallel planes through the fiber strands 141 and 143, which are oriented so as to be mutually parallel, as well as a fiber strand 142 which interconnects the two planes.

By contrast, FIG. 10 shows the cured fiber strands 141, 142, and 143 of the console from the preceding figures, without the functional elements.

The steering-column assembly according to the invention having the fiber-composite material console 55 is shown in FIG. 11. The integrated functional elements 13 serve as bearings 20 for the pivot axis of the pivot lever 4, and as fastening elements 77 for fastening the console 55 to the body (not shown here), and for the guide elements of the fixing system 90.

As opposed to steering columns of the generic type as illustrated in FIG. 1, the steering-column assembly according to the invention from FIG. 11, on account of the employment of fiber-composite materials, has a low weight, wherein adequate strength and rigidity are achieved, or even increased strength and rigidity are achieved.

The savings in weight lead to a favorable influence on fuel consumption and to an increase in the range of electric cars. On account of the design which is appropriate for the flux of force, and of the high strength in the fiber direction, the installation space can be kept small. Furthermore, the natural frequency of the steering-column assembly is positively influenced on account of the increased rigidity of the console, such that vibrations of the steering wheel, which are transmitted by the steering column, are significantly minimized, so as to improve the comfort features when driving.

In one other exemplary embodiment (not illustrated here), the pivot lever is manufactured from a fiber-composite material, according to the method described above. All components of the steering-column assembly may be wholly or partially manufactured from a fiber-composite material.

The material properties may be varied in a wide range by the choice of fibers. Carbon fibers, aramid fibers, and/or glass fibers are preferably used individually or in combination.

As has been described earlier, preimpregnated fibers are preferably used. Preimpregnated fibers have a thermoplastic or duroplastic impregnation. The fibers which have been provided with a thermoplastic impregnation in a combination with carbon fibers and/or glass fibers, for example, may advantageously be processed to form a hybrid yarn. In one exemplary embodiment it is provided here that the hybrid yarns during the winding process are heated, such that the thermoplastic fibers are fused and form a matrix of the composite already during winding. The shape of the workpiece may be adapted thereafter by compression in a mold. Fusing of the thermoplastic fibers after the winding process in an oven, or in a heated mold, and/or by the thermoplastic injection-molding method is also possible.

One other exemplary embodiment provides fibers which are not preimpregnated. These fibers are wound as has been described in the earlier exemplary embodiments. After the winding process the mold is assembled, or the workpiece together with the winding core is placed in a mold, and the mold is injected with thermoplastic or duroplastic resin, and the workpiece is cured. All forms of the resin transfer molding (RTM) method are provided for the use of a duroplastic matrix. As opposed to compressing, the matrix compound here is injected by means of a piston from an antechamber, which most often is heated, via distributor ducts into the mold, wherein said matrix compound is cured by heat and pressure.

In order to remove the cured console from the mold, the plates of the mold are also pulled apart here and the winding spools are pulled toward the inside into the mold.

In one further embodiment it is provided that the mold, prior to or after adding resin, is placed into an injection-molding machine, and that the workpiece for further shaping is injection-molded or back-injection molded, using thermoplastic or duroplastic injection molding.

Another exemplary embodiment discloses that the winding, which is appropriate for the flux of force, of fibers is carried out on auxiliary materials, such as, for example, plastic-material fabrics or cross-laid structures, or woven fabrics made from reinforcement fibers, which keep the fibers in shape and position until the latter are fixed by way of a matrix. These fibers, when woven fabrics or cross-laid structures are used, likewise form a fiber composite with the matrix, which serves for absorbing basic loads, for inducing loads, or as a load-free structure.

The steering-column assembly has components according to the invention, which are represented in an individually molded manner by way of fiber technology, having high strength properties and high rigidity properties, and a low weight. The method according to the invention furthermore enables a defined conception of such components, which is appropriate for the flux of force.

LIST OF REFERENCE SIGNS

-   1. Steering column -   2. Steering spindle -   3. Steering column tube -   4. Pivot lever -   5. Console -   6. Control-rod part -   7. Fastening point -   8. Cardan joint -   9. Tension bolt -   10. Tension lever -   11. Winding core -   12. Winding spool -   121. Winding spool -   13. Functional element -   14. Fiber -   141. Fiber strand -   142. Fiber strand -   15. Supply package -   16. Impregnation unit -   17. Guide unit -   18. Mold -   19. Boards -   20. Bearing -   55. Console -   77. Fastening elements -   90. Fixing system 

1.-10. (canceled)
 11. A method of manufacturing a fiber composite component, the method comprising: winding fibers along predetermined tracks about at least one winding spool of a winding core; introducing a curable resin into the fibers or a mold that receives the fibers wound about the at least one winding spool; curing the curable resin to form the fiber composite component; removing the at least one winding spool from the fiber composite component by moving the at least one winding spool inwardly into the winding core; and removing the winding core and releasing the fiber composite component.
 12. The fiber composite component according to the method of claim
 11. 13. A method of manufacturing a fiber composite component, the method comprising: winding fibers along predetermined tracks about at least one winding spool of a winding core, wherein the fibers are soaked with a curable resin; curing the curable resin to form the fiber composite component; removing the at least one winding spool from the fiber composite component by moving the at least one winding spool inwardly into the winding core; and removing the winding core and releasing the fiber composite component.
 14. The method of claim 13 further comprising: positioning one or more operative elements at predetermined points on the winding core prior to winding the fibers along the predetermined tracks; and connecting the one or more operative elements to the fibers such that the one or more operative elements and the fiber composite component form an integral component.
 15. The method of claim 13 further comprising applying an auxiliary material onto the winding core prior to winding the fibers along the predetermined tracks, wherein the auxiliary material is configured to maintain a shape and a position of the fibers until the fibers are fixed by curing the curable resin.
 16. The fiber composite component according to the method of claim
 13. 17. The fiber composite component of claim 16 wherein the fiber composite component is comprised of a plurality of types of fiber structures having identically oriented fibers.
 18. The fiber composite component of claim 17 wherein the fiber composite component is made using the winding core, wherein the winding core is separated from the fiber composite component prior to fitting the fiber composite component in an assembly, wherein the winding core is not included in the assembly.
 19. The fiber composite component of claim 18 wherein the fiber composite component comprises a plurality of operative elements that are fixedly connected to the fiber composite component by way of the winding of the fiber and the curing of the curable resin.
 20. The fiber composite component of claim 19 wherein the plurality of operative elements are selected from a group including fastening elements, guides, motion limiters, bearings, and brackets for wiring looms.
 21. The fiber composite component of claim 19 wherein the fiber composite component is positioned in and/or along a flux of force of a motor-vehicle superstructure and of a motor-vehicle body, wherein the fiber composite component is formed from fiber-reinforced plastics material in which the fibers are wound. 